Reproduction apparatus using photovoltaic material

ABSTRACT

Apparatus for the reproduction of visual images which uses a layer of photovoltaic material deposited on a substrate in such a way as to substantially increase the voltage produced when exposed to light according the pattern of an image to be reproduced so that no external charging voltage is required. The application of a toner to the material develops the image which may then be transferred to a copy sheet to reproduce the image. After discharge, either naturally by the passage of time or intentionally, the material may be exposed once again to permit the reproduction of a new image.

l Umted States Patent [151 3,647,286

Delorme, Jr. 1 Mar. 7, 1972 [54] REPRODUCTION APPARATUS USING 2,990,2806/1961 Giaimo ..355/1 7 X PHOTOVOLTAIC MATERIAL 3,185,051 5/1965 Goffe..355/3 3,199,086 8/1965 Ka11mann.... 355/17 X [72] lnventor: John H.Delorme, Jr., 6826 North Wayne, 3 226 253 12/19 5 gobrechtw 1 7 0 XChICag 60 6 3,254,998 6/ 1966 Schwertz ..355/ 17 [22] Filed: ML 10 19693,498,835 3/1970 Chiang ..1 17/107 X [21] App1.No.: 797,729 PrimaryExaminerJohn M. l-loran Assistant Examiner-Monroe H. Hayes 52 us. Cl..3ss/17, 96/1 Hersh and 1 III. [58] Field olSeareh ..355/3, 17;96/1, 1A, 1 PC; l

' 117/106 R 07 .Apparatus for the reproduction of visual images whichuses a layer of photovoltaic material deposited on a substrate in such56] R f e Cited a way as to substantially increase the voltage produced.when

exposed to light according the pattern of an image to be UNITED STATESPATENTS reproduced so that no external charging voltage is required. Theapplication of a toner to the material develops the image 2,453,76311/1948 Smith ..117/106 X which may then be transferred to a copy She?tto reproduce 258L460 H1952 Vangeen'" ""117/106 the image. Afterdischarge, either naturally by the passage of 2'624'652 H1953 i "355/17X time or intentionally, the material may be exposed once again2,654,853 10/ 1953 We1mer.... ..l 17/ 107 UX to permit the reproductionofa new image 2,829,025 4/1958 Clemens ..355/3 X 7 2,860,221 Kohl ..117/107 2 Claims, 5 Drawing Figures REPRODUCTION APPARATUS USINGPHOTOVOLTAIC MATERIAL BACKGROUND OF THE INVENTION development in recentyears. The processes and apparatus in use to date have usedphotoconductive materials which are charged in an overall pattern bycorona discharge from an electrostatic source. Thereafter the charge isdestroyed or removed from portions exposed to light through or reflectedfrom animage such as the original copyof a document to leave a latentelectrostatic image can be transferred to a copy sheet brought intosurface contact with the developed image by reversal of theelectrostatic charge or by'providing a copy material having an adhesivecoat.

Other approaches in this art. have involved the use of photosensitivematerials which, while they do not require the surface of the materialto be charged as by the use of a corona, but nevertheless still requirethe provision of a voltage source in order to produce latentelectrostatic images when the material is imaged by selective radiation.

The necessity for a voltage source to charge a surface or produceselective polarization of the photosensitive material when it is exposedto light introduces an expense and structural complications in apparatusbuilt for these purposes. Furthermore, it restricts the use of suchapparatus to essentially stationary equipment thus precluding the use ofelectrostatic copying process in hand and other portable cameras.

Therefore it is an object of this invention to provide a novelelectrostatic method of and apparatus for the reproduction of imageswhich does not require a voltage source to charge or otherwise conditiona photosensitive material and consequently is relatively simple in itsconstruction and may be utilized in relatively portable systems.

These and other objects are achieved by the use of a photovoltaicmaterial deposited on a substrate in such a way that repetitive faultsor discontinuities appear therein, providing means for exposing thesurface to transmitted or reflected light from an imageto be reproducedand then developing and transferring the latent electrostatic imageformed on the surface of the material.

BRIEF DESCRIPTION OF THE DRAWINGS These and other objects and advantagesof this invention will hereinafter appear and, for purposes ofillustration but not of limitation, embodiments of the invention aredescribed and shown in the accompanying drawings in which:

.FIG. 1 is a diagrammatic illustration-showing how suitable photovoltaicmaterial may be deposited on substrate for use in the invention;

FIG. 2 is a diagrammatic illustration of apparatus embodying theinvention effective to carry out one of the steps thereof;

FIG. 3 is a diagrammatic illustration of apparatus embodying theinvention effective to carry out another of the steps thereof;

FIG. 4 is an illustration of the manner in which still another step ofthe invention may be carried out; and

FIG. 5 is an illustration of the reproduction of an image using themethod and apparatus of the invention.

Photovoltaic materials are those which generate an electromotive forcewhere their surface is exposed to illumination. This phenomenon has beenknown for some time. However, the voltages generated have been, untilrelatively recently, quite small so that the use of such materials hasbeen limited. The low values of voltage available has been due in largepart to the method of fabricating such surfaces. However it is now knownthat if a material capable of photovoltaic activity is deposited on asubstrate when the substrate is in a plane maintained at an angle with aline passing through a source of the material in an evaporator theavailable voltage can be increased significantly. Descriptions oftechniques and analyses of the result of the method of photovoltaicmaterial are to be found in the following articles: High Photovoltagesin Cadmium Sulfide Films by Brandhorst et al.; NASA Technical NoteD-3447, Acquisition No. N66-23455, April, 1966; Unusual Photovoltages inEvaporated Layers of Germanium by Kallmann et al.; ACTA PhysicaPolonica, Vol. 25, pp. 67l-678, 1964, High Photovoltages in Silicon andSilicon Carbide Films and Their Origin from a Trap-Induced Space Chargeby Brandhorst et al.; Journal of Applied Physics, Vol. 35, No. 7, pp.1997-2003, July, 1964.

A summary of the contents of these publications teaches the depositionof a suitable material such as germanium, silicon, silicon carbide,cadmium sulfide, and others may take place when a source of suitablematerial is provided in a crucible to be heated in a vacuum and disposedbeneath a substrate material. A metallic shield is interposed betweenthe source and the substrate to control material.

This is illustrated in FIG. 1 wherein a crucible 2 holding a source ofsuitable material is disposed beneath a metallic shield 4 having anopening 6 therein. A substrate 8, which may be of a metallic orconducting material, is maintained so that its centerline I0 is at anangle 6 to a line 12 extending perpendicularly through the crucible 2.The above-cited articles present values for the vacuum which should bemaintained and show a range of 10 to I0 torr. The thickness of thedeposited layer may vary from 0.5 to 50 microns, and it may have aresistivity greater than l0 ohm/cm. The angle between the plane of thesubstrate and a line through the crucible will vary depending on thematerial used and may vary from l0 to 60". It should be noted that inorder to achieve voltages higher than those of the band gap of thematerial the deposition should not take place at right angles. This isbecause, in accordance with one theory of explanation, deposition at anangle results in the material being deposited with repetitive stackingfaults" or as though it were a large number of individual crystalsrather than one single crystal.

In addition to the materials noted above and in the referenced articlesa wide variety of materials capable of photovoltaic activity may beused. These would include ZnS, ZnSe, ZnTe, CdSe, CdTc, Sb, SbS, SbTe,Se, Bi, BiS, and BiTe.

A process and apparatus for the reproduction of images usingphotovoltaic materials is illustrated in FIGS. 2 through 4. Theseillustrations are diagrammatic, for it is clear that a large number ofvariations in the particular apparatus used are possible and theparticular ones selected are well within the choice of designers workingwithin this field.

In FIG. 2 a layer 14 of photovoltaic material has been deposited on thesubstrate 8 in accordance with the process described so as to constitutean exposure plate which may be positioned by any desirable meanssuitably spaced from an original the image of which is to be reproduced.The original 16 may'take the form of a document bearing text material,photographs, drawings, or the like. It should be understood that it isconsidered within the scope of invention disclosed the original may be athree-dimensional object so that the process and apparatus may be usedin what are considered devices of the class of cameras.

Regardless of the form of the original 16 it will include relativelydark areas and relatively light areas indicated by reference numerals l8and 20, respectively. Visible light may be provided by sources 22 whichwhen activated will provide a source of light to be reflected from theoriginal I6. The reflected light is focused by a suitable opticalsystem, including lenses and represented diagrammatically by the lens atthat a corresponding area 26 on the surface of the layer 14 will developlittle or no voltage while the relatively light areas will reflectgreater light and the corresponding area 28 on the surface of layer 14will develop greater voltages. As may be seen in the referenced articlesthe voltages developed are negative; i.e., the voltage at the surfacewhich is that portion of the layer closest to the material source duringformation of the layer are negative with respect to the materialadjacent the substrate. Thus in the embodiment of FIG. 2 the areas 26will be positive with respect to areas 28.

By further reference to the articles cited, if the light is removed acertain amount of time will be required for the generated voltages to bedischarged for they will decay exponentially over a period of at leaston the order of ten seconds or more.

During this period where the voltage appears on the surface of the layer14 that latent electrostatic image of the original that has been createdmay be developed to present a visible image that can be transferred orotherwise caused to be printed on suitable copy paper.

The developing phase is effected by the apparatus of FIG. 3 showing asource 32 of charged electroscopic or toner material from which thesurface of the layer 14 is dusted or coated. If it is desired to producea positive image the toner material selected will be positively chargedso that upon its application to the surface it will be attracted to thenegatively charged portions of the surface. Alternatively if a negativeis desired a negatively charged toner would be used.

In order to reproduce the image on a copy sheet for use, such a sheet 34coated with adhesive material may be brought into contact the nowdeveloped surface of the layer 14 to transfer the image formed by thetoner pattern to the copy sheet. HO. 5 illustrates a copy of an originalappearing on a copy sheet 34.

As has been set out above it is contemplated that a large number ofvariations in the specific apparatus are using those elements well knownin the art of electrostatic copying. For instance, the surface 14 couldbe formed on a drum shaped substrate and rotate from exposure todeveloping and then to printing positions. Other variations in theapparatus include depositing the photovoltaic material on a conductiveweb substrate and move it to exposing, and developing positions toproduce a negative which could be severed from the web and used in otherequipment as a master.

Thus it will be understood that any number of changes may be made in thedetails of construction, arrangement, and operation without departingfrom the spirit of the invention, especially as defined in the followingclaims.

What I claim and desire to secure by Letters Patent of the United Statesis:

1. Apparatus for reproducing visual images comprising: a substrate; alayer of photovoltaic material on said substrate having repetitivestacking faults therein; means for projecting an image to be reproducedonto said material to expose said material to a light pattern of theimage thereby to produce a voltage pattern on said material conformingto the image; and means for applying a developing substance to saidmaterial whereby said substance assumes a pattern conforming to thevoltage pattern.

UNITED STATES PATENT OFFICE v p CERTIFICATE CORRECTION Patent No.3,647,286 Dated March 7, 1972' Inventor(s) John H. DeLorme, 'Jr I I 7 Itis certified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Columh 1, line 17, after "image" insert --which can be developed by asuitable pigment powderor toner. The

toneron the developed image-.

Signed and sealed this 22nd day of August 1972.

" (SEAL) Auoest;

EDWARD M FLETCHER JR ROBERT GOTTSCHALK Attest ins Off icer Commissioner.of Pat ent s FORM PO-1050 (10-69) co 0375-p5 u.s. GOVERNMENT PRINTINGorncz: was 0-366-334 UNITED STATES PATENT FFTQE v CERTIFICATE OFCORREQTION Patent No. 3,647,286 Dated March 7, 1972 Inventor(s) John H.DeLorme, Jr.

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 1, line 17, after "image" insert --which can be developed by asuitable pigment powderor toner. The

toner on the developed image-.

Signed and sealed this 22nd day of August 1972.

(SEAL) At t eSt: I

EDWARD M. FLETCHER,JR. ROBERT GOTTSCHALK N Commissioner, of Patents:

Attesting Officer FORM PO-105O (10-69) co c 60375-1369 2' u.5 GOVERNMENTPRINTING OFFICE: I969 0-366-334

1. Apparatus for reproducing visual images comprising: a substrate; alayer of photovoltaic material on said substrate having repetitivestacking faults therein; means for projecting an image to be reproducedonto said material to expose said material to a light pattern of theimage thereby to produce a voltage pattern on said material conformingto the image; and means for applying a developing substance to saidmaterial whereby said substance assumes a pattern conforming to thevoltage pattern.
 2. The apparatus of claim 1 including means fortransferring the image formed by the developing substance to a copymaterial.